Many applications exist for probing a device by making temporary contact with the device. For example, probes may be used to monitor operation of a device. As another example, an electronic device may be tested by probing the electronic device to establish temporary electrical connections with the device. Test data may be input to the device via the temporary connections, and response data generated by the device may be read also through the temporary connections. A probe card apparatus typically includes an array of probes that are electrically connected through a support structure to interface terminals to, for example, a tester. Often the probes, are compliant, that is, the probes deflect in response to a force.
In many probing applications, a particular level of compliance is desirable. For example, it may be desirable for the contact tips of the probes to displace a particular, predetermined distance per unit of force applied to the contact tips and to allow for a maximum deflection. Compliance may be quantified as spring constant expressed as unit of applied force per unit of deflection.
In a probing application, there may be a maximum deflection that can be applied to the probes, which results in a maximum allowable force exerted by the probes. For example, there may be a limit to the deflection that the probes can experience before a permanent deformation of the probes occurs. Permanent deformation may not be acceptable in many applications. In metallic materials, permanent deformation may occur once the probe is stressed near or above its elastic limit.
In existing probe card apparatus, the compliance of the array of probes typically dominates compliance contributions from other parts of the probe card apparatus. In fact, in designing a probe card apparatus, the compliance contribution of other parts of the probe card apparatus has traditionally been ignored. There are at least two potential disadvantages to considering only the compliance contribution of the probe array in designing and making a probe card apparatus. First, if only the compliance of the probe array is considered, the probe array must be designed to provide all of the desired compliance of the probe card apparatus. Generally speaking, the greater the compliance needed from the probe array, the larger the probes in the array need to be, and the greater the pitch or minimum spacing must be. Thus, the desired compliance level of the probe card apparatus may indirectly set a minimum size and pitch for the probe array, even though, in some applications, smaller probes and tighter pitches may be desirable or needed. Second, because other sources of compliance are not considered but nevertheless may be present, the overall compliance of the probe card apparatus may not be as accurate as expected if only the compliance of the probe array is considered when designing and making a probe card apparatus.
There is, therefore, a need for improvements in designing and making a probe card apparatus.